SMD = Surface Mounted Devices. A method for constructing electronic circuits in which the components are mounted directly onto the surface of printed circuit boards (PCBs). An electronic device so made is called a surface-mount device (SMD).

Through hole = construction method of fitting components with wire leads into holes in the circuit board. Both technologies (SMD and through hole) can be used on the same board for components not suited to surface mounting such as transformers and heat-sinked power semiconductors.